1. Field of the Invention
The present invention relates to a conveying apparatus (and, more generally, a parts handling apparatus) that conveys electronic parts such as chip-type capacitors and resistors, and a method for use thereof.
2. Description of the Related Art
Japanese Examined Patent Publication No. 2-20490 discloses a conveying apparatus that automatically stores electronic parts on a carrier tape fed by a parts feeder. This conventional conveying apparatus feeds electronic parts, conveyed by means of vibration, from a feed track of the parts feeder into pocket slots formed on the entire circumference of a gear-like conveying ring. The apparatus then loads the electronic parts into concave sections of a carrier tape and applies an adhesive cover tape onto the carrier tape. The conventional apparatus has, between an exit end of the feed track of the parts feeder and the gear-like conveying ring, a guiding support plate grooved for engagement with teeth of the conveying ring. The apparatus also has vacuum paths with outer ends having suction holes. Using the above-described structure, this conventional conveying apparatus feeds the electronic parts in the pocket slots through the feed track.
In the related art, however, the conveying apparatus causes the following problems. While the electronic parts stored in the pocket slots are being conveyed, the lower surfaces of the electronic parts slide in contact with the upper surface of the guiding support plate. When the electronic parts having outer electrodes at both ends are being conveyed, abrasions and scratches may be caused on the lower surfaces of the outer electrodes. The abrasions and scratches can also be caused on the end surfaces of the outer electrodes because these surfaces may slide in contact with the inner-circumferential surface of the guiding support plate during the rotation. This can easily occur during the conveying operation despite the use of an arcuate inner-circumferential surface of the guiding support plate designed to prevent the electronic parts from being propelled in the outer-peripheral direction.
During the conveying operation, for measurement of electrical characteristics of the electronic parts, the electronic parts need to be precisely positioned in the pocket slots. However, reliably setting contact electrodes in contact with outer electrodes of the electronic parts has been difficult because parts that are offset in the outer-peripheral direction are unstable because of the centrifugal force caused by the rotation of the gear-like conveying ring. Offset limits are strict; for example, for an electronic part of less than a few millimeters in size, even an offset of one millimeter may not be tolerated.
An object of this present invention is to provide an apparatus for conveying (and, more generally, handling) electronic parts (such as chip-type electronic parts), whereby damage to the electronic parts can be reduced, and also the positions of the electronic parts during a conveying operation can be stabilized.
To achieve these objectives, according to one aspect of the present invention, there is provided a conveying table which is rotationally driven in a constant direction. The table includes a plurality of concave storage slots formed with identical pitches on the table""s entire outer-peripheral section. These slots store chip-type electronic parts, each slot having a bottom surface, two radial side surfaces, and an inner-circumferential side surface. Further, an air hole (i.e., a conduit) is provided, having one end open on the inner-circumferential side surface and the other end communicatively connected with a negative air pressure source generating negative suction air pressure that sucks the electronic part onto the inner-circumferential side surface of the concave storage slot.
An electronic part is fed by a feed mechanism (such as a parts feeder) located in a section near the outer-peripheral section of the conveying table. The electronic part is then vacuum-suctioned by negative air pressure provided through the air hole onto the concave storage slot. In this state, one end surface of the electronic part abuts the inner-circumferential side surface. When the table rotates, the electronic part would normally move in the outer-peripheral direction due to the centrifugal force created by the rotation. In the present invention, however, because the electronic part is vacuum-suctioned through the air hole onto the inner-circumferential side surface, the electronic part is not offset when the table rotates. This mechanism thereby facilitates the measurement of electrical characteristics of the electronic parts, allowing contact electrodes of a measurement device to precisely contact outer electrodes of the electronic part.
Vacuum-suction can be employed according to two timing methods; a continuous method and a periodic method. In the continuous method, the electronic parts are kept suctioned in the storage slot during the rotation of the conveying table. In the periodic method, the electronic parts are periodically suctioned in the storage slots during periods when the rotation stops. The periodic method is performed by intermittently rotating the conveying table and allowing the rotation to periodically stop to measure characteristics of the electronic parts. One component-related difference between the two methods is that the continuous method does not require a guard for preventing the electronic parts from being radially propelled outward.
According to another aspect of the present invention, there is provided a concave storage slot having a bottom surface, two radial side surfaces, and an inner-circumferential side surface. Due to this structure, the electronic part stored therein does not slide in contact with other parts, thereby reducing the potential of damage to the outer electrodes of the electronic part.
In a preferred embodiment of the present invention, a selector mechanism is installed so that one end of the air hole communicates through a selector valve with a negative air pressure source and a positive air pressure source (which generates compressed air to eject the electronic parts). In this way, ejection of the electronic parts in the peripheral direction of the conveying table is facilitated when it is desired that the electronic parts be ejected after the table is rotated to a predetermined position. In this case, the electronic parts can be ejected by application of compressed air from an outside mechanism, but it is difficult to effectively apply the compressed air to an end surface of a target electronic part. However, as described above, making use of the air hole enables precise application of the compressed air at the end surface of the electronic part, facilitating ejection of the electronic part from the concave storage slot.
Another preferred embodiment of the present invention is that the conveying table is xe2x80x9cblock-constructedxe2x80x9d including an upper plate and a lower plate. In this construction, the upper plate is formed so that it has notches with identical pitches on its outer-peripheral section, and a lower plate is fitted on a lower surface of the upper plate so as to close the lower portions of the notches. Further, the lower surface of the upper plate is grooved (with the grooves extending to the inner-circumferential side surface of the notch) so that the air hole is thereby formed.
The block construction is preferable to the above-described integral slot/hole arrangement because the block construction is easier to manufacture. This is especially true in manufacturing a conveying table that handles smaller electronic parts, wherein many concave storage slots must be formed, each having a width of one to several millimeters, and even smaller air holes on the inner-circumferential side surfaces of the slots must be provided.
As mentioned above, considering the manufacturing difficulties of the integrated design, it is easier to construct the conveying table by separating it into blocks comprising an upper plate and a lower plate, forming the gear-like notches on the upper plate, and making the grooves which will form the air holes on the upper plate. There are other reasons why it is easier to construct the table in blocks. For example, the upper plate can be integrally made of resin, and the lower plate can simply be in a disc form, which can be relatively easily manufactured.
The electrical characteristics of the electronic parts having the outer electrodes are measured during the conveying operation. In this case, ordinarily a pair of pin-type contact terminals of a measurement device are pressed onto the outer electrodes of the electronic part so as to form electrical conduction therewith. However, while this technique is viable, the outer electrodes may be damaged in this method.
For preventing possible damage as mentioned above, a pair of the contact electrodes contacting the outer electrodes of the electronic part, respectively, are formed on the bottom surface of the individual concave storage slots of the conveying table. In this method, when the electronic part is pushed by an insulated cushioned member from the upper side of the part, the outer electrodes and the contact electrodes of the electronic part can be reliably placed in electrical conduction with each other. If the contact electrodes are connected to the measurement device, the electrical characteristics of the electronic parts can easily be measured, and possible damage to the electronic parts can be prevented or reduced.
In a section near the peripheral section of the conveying table, a taping mechanism is provided to apply an adhesive cover tape onto a carrier tape after the electronic parts ejected from the concave storage slots are stored in storage sections of the carrier tape. The procedure from conveying through taping is thus automated, thereby greatly improving the operational speed of this procedure, as well as reducing the size and cost of the facilities used to perform these functions.
Another possibility is that instead of the taping mechanism, a package-in-case mechanism is provided, which packages multiple electronic parts ejected from the concave storage slots into cases on the basis of a predetermined quantity.